Orthokeratology lens with displaced shaping zone

ABSTRACT

A contact lens for application in practice of orthokeratology on an eye, including a curved shell having a concave surface and a convex surface. The concave surface includes a carrier zone and a back shaping zone, the back shaping zone having a first curvature and the carrier zone having at least one second curvature. The curved shell has a geometric center and the back shaping zone has a shaping zone center and the back shaping zone center is offset peripherally from the geometric center. The curved shell can have an overall diameter that approximates a corneal limbal diameter of the eye to which the contact lens is to be applied.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 15/598,384,filed May 18, 2017, entitled “Orthokeratology Lens with DisplacedShaping Zone”, which is a continuation of application Ser. No.14/644,860 filed Mar. 11, 2015, entitled “Orthokeratology Lens withDisplaced Shaping Zone”, now U.S. Pat. No. 9,709,822, issued Jul. 18,2017, each of which is hereby fully incorporated herein by reference.

TECHNICAL FIELD

The invention generally relates to the field of contact lenses. Moreparticularly, the invention relates to contact lenses that are appliedto the eye in the practice of orthokeratology to temporarily reshape theanterior corneal surface.

BACKGROUND

Orthokeratology is the practice of applying rigid generally highlyoxygen permeable contact lenses to the eye to reshape the anteriorcorneal surface, thus altering refractive error temporarily or possiblypermanently. Orthokeratology is sometimes identified by other names suchas corneal shaping contact lenses, overnight vision correction,overnight contact lenses to correct or control myopia, or cornealrefractive therapy. Other identifiers beyond these may be utilized aswell. Orthokeratology is used primarily in the treatment of myopia ormyopia with astigmatism. However, orthokeratology has also beenutilized, less commonly, in the refractive treatment of hyperopia orhyperopia with astigmatism.

Orthokeratology has existed in some form for many decades. Early, hardcontact lenses were noted by many to temporarily alter the anteriorcorneal shape, thus, creating alterations in refractive error when thecontact lenses were not on the eye. Early attempts to practiceorthokeratology utilizing hard (PMMA or polymethyl methacrylate) contactlenses were hindered by poor technology and limited understanding ofcorneal physiology and the criteria necessary to predictably correct formyopia by corneal molding. Significant advances have been made in thepractice of orthokeratology since the advent of corneal topographymeasuring instrumentation in approximately the last twenty years. Theadvent of computerized corneal topography has permitted the creation ofcontact lens designs for orthokeratology that provide betterrepeatability and predictability of results because the cornealtopographer provides an increasingly accurate map of the surfacecurvature of the cornea.

Further improvements in orthokeratology occurred in recent years becauserigid gas permeable contact lenses that provides a much higher oxygenpermeability have demonstrated the possibility of wearing theorthokeratology lenses overnight rather than utilizing the contactlenses during the day. Further, the introduction of computer numericallycontrolled precision lathes and other manufacturing equipment haveallowed lens designs for orthokeratology to be manufactured to higheraccuracy than previously possible.

Orthokeratology has also been credited by some researchers with slowingor reducing progression of myopia in children. Results of research onthis area have been mixed and the effectiveness of orthokeratology inlimiting or slowing the progression of myopia is uncertain.

Because the cornea provides a large fraction of the eye's focusingpower, and because of the high refractive power and steep curvature ofthe cornea, very small changes in the curvature of the cornea or cornealthickness can result in substantial changes in refractive error.Accordingly, in orthokeratology, specially shaped contact lenses areused to lightly press on or mold the cornea, causing the cornea togradually change shape to correct refractive error. The correctiveeffect may last up to approximately 72 hours once the eye is initiallyadapted to the lenses. Accordingly, in a usual orthokeratologyprocedure, according to current practice, contact lenses are worn duringsleep and removed during the day. The corneal molding effect after thelenses are removed provides a reduction or elimination of refractiveerror. Typically, the rigid high oxygen permeability contact lenses areworn for six to eight continuous hours during sleep. Sometimes softcontact lenses are worn during the day at least during the adaptationperiod for correction of residual refractive errors. Some patientsexperience a return of some refractive error in the evening for whichthe orthokeratology lenses or soft contact lenses may be worn to correctrefractive error under these circumstances.

Improvements in the accuracy of corneal topography analysis have alsoprovided additional information about the shape of the anterior corneaand has made it apparent that the optical center of the cornea does notalways coincide with the visual axis or optical axis of the eye.

There is still room for improvement in the area of orthokeratologycontact lenses.

SUMMARY

The invention disclosed and claimed in this application addresses aproblem apparent in certain orthokeratology circumstances.

Example embodiments of the invention include a high oxygen permeabilityrigid gas permeable contact lens for orthokeratology that is sized toapproximate the limbal diameter and that has a displaced molding zone ascompared to the geometric center of the contact lens. According toembodiments of the invention, the displaced molding zone orthokeratologylens may include a curved shell having a concave surface and a convexsurface. The concave surface includes at least a carrier zone and amolding zone. The molding zone is on the concave surface of the shelland has a first curvature and the carrier zone has at least one secondcurvature, possibly one or several additional curvatures.

According to an embodiment of the invention, the curved shell has ageometrical center centered on the perimeter of the circular lens andthe molding zone has a molding zone center that is displaced from thegeometrical center. As discussed above, the curved shell may have anoverall diameter that approximates the corneal limbal diameter of theeye to which the contact lens is to be applied.

According to embodiments of the invention, the curved shell isstructured to be stabilized in rotation relative to the eye to when thelens is worn on the eye during sleep.

The above summary is not intended to describe each illustratedembodiment or every implementation of the subject matter hereof. Thefigures and the detailed description that follow more particularlyexemplify various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter hereof may be more completely understood in considerationof the following detailed description of various embodiments inconnection with the accompanying figures, in which:

FIG. 1 is a cross-sectional view of the anterior segment of a human eye;

FIG. 2 is a cross-sectional view of the anterior segment of the humaneye with a schematically depicted orthokeratology lens in place;

FIG. 3 is a cross-sectional view of the anterior segment of the humaneye schematically depicting the effect of an orthokeratology lens on theshape and structure of the human cornea with corneal changes exaggeratedfor clarity;

FIG. 4 is an anterior to posterior view of an orthokeratology lensaccording to an embodiment of the invention including a displacedmolding or shaping zone;

FIG. 5 is an anterior to posterior view of an orthokeratology lensaccording to an embodiment of the invention including orientationfeatures of the lens;

FIG. 6 is anterior to posterior view of an orthokeratology lensaccording to an embodiment of the invention including a displacedmolding or shaping zone; and

FIG. 7 is a cross sectional view of an orthokeratology lens according toan embodiment of the invention.

While various embodiments are amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the claimedinventions to the particular embodiments described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the subject matter as defined bythe claims.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 1-3, orthokeratology lens 20 is schematicallydepicted along with eye 22. Eye 22 includes an anterior segment 24 whichfurther includes cornea 26. Cornea 26 has multiple layers and astructure familiar to those skilled in the art. The eye's structureincludes corneal epithelium 28. According to recent theories of themechanism of action of orthokeratology, orthokeratology lens 20 providesa positive pressure on the tear film 30, centrally and a neutral ornegative pressure peripherally. In the context of orthokeratologycorrection for myopia, this causes compression of central cornealepithelium 28 and reorganization of corneal epithelial cells such thatthe corneal epithelial cells are displaced more peripherally and lesscentrally, thus subtly reshaping the anterior corneal epithelium 28surface resulting in a change in refractive error. In the context ofhyperopia orthokeratology correction, pressure is applied to the cornealepithelium more peripherally and less centrally thus causing migrationor remodeling of corneal epithelial cells to create a steepening ratherthan a flattening of the anterior cornea. Known orthokeratology lensdesigns include a molding or shaping zone that is located centered inthe rigid oxygen permeable contact lens.

Referring now to FIGS. 4 and 7, displaced molding zone contact lens 32according to an example embodiment of the invention is depicted.Displaced molding zone contact lens 32 is a generally unitary structureformed of rigid curved shell 34 forming lens body 36. Rigid curved shell34 is formed, for example, from a high oxygen permeability gas permeablerigid contact lens material. According to an example embodiment of theinvention, rigid curved shell 34 is intended for overnight wear andaccordingly, is formed of an oxygen permeable material having anISO/Fatt Dk of 85 or more. Rigid curved shell 34 is generally formed ofa material approved for overnight wear by the U.S. Food and DrugAssociation. For example, rigid shell 34 may be formed of asiloxane-fluorocarbon polymer. Lens materials may also include otherfluorocarbon polymers and any rigid oxygen permeable contact lensmaterial now available and materials to become available in the future.

Lens body 36 is defined by peripheral edge 38, anterior convex surface40 and posterior concave surface 42. Peripheral edge 38 defines overalldiameter 44 of displaced molding zone contact lens 32. According to anexample embodiment of the invention, overall diameter 44 approximatesthe limbal diameter 46 of cornea 26. Accordingly, overall diameter 44,according to an example embodiment, is approximately 11.5 mm but mayrange from approximately 10.5 mm to approximately 12.5 mm. Thesediameter values are examples and should not be considered limitingunless recited in the claims. Human cornea 26 is generally understood tohave a horizontal diameter in a range of 10.76 mm to 12.60 mm and avertical diameter in a range of about 10.6 mm to about 11.7 mm. Cornealdiameter is commonly measured based on the so-called horizontal visibleiris diameter (HVID) which is the measured width of the transparentcornea horizontally across the cornea from the white edge of the scleratemporally to the white edge of the sclera nasally. According to exampleembodiments of the invention, overall diameter 44 may range betweenapproximately 10.5 mm and 13 mm.

Displaced molding zone of contact lens 32, according to an exampleembodiment of the invention, may be manufactured in a reverse geometrydesign. Reverse geometry designs include lenses of three zone and fourzone designs. These terms are understood by those skilled in theorthokeratology arts.

According to an example embodiment of the invention, referring to FIGS.4 and 7, rigid curved shell 34 of displaced molding zone contact lens 32presents concave surface 42 back shaping zone 48, second curve 50,optional third curve 52 and fourth or peripheral curve 54. Rigid curvedshell 34 presents geometric center 56. As can be seen in the depictedembodiment, shaping zone center 58 is displaced from geometric center 56as is second curve 50.

Base curve 60 of back shaping zone 48 is generally formed to be 0.30 to1.40 mm flatter than the flattest corneal curvature, also known as theflattest K. Back optic zone diameter 62 of back shaping zone 48 can beof any diameter but generally will fall within the range of 6.0 to 8.0mm.

Second curve 50 also sometimes referred to as a reverse curve, generallyhas a width of 0.5 to 1.0 mm and is curved to be 0.5 to 1.0 mm steeperthan base curve 60. This is the equivalent of approximately 3 to 5diopters steeper than base curve 60. Optional third curve 52, ifpresent, is also sometimes referred to as an alignment zone. Third curve52, if present, according to an example embodiment of the invention is1.0 to 1.5 mm wide.

Fourth or peripheral curve 54 is generally flatter than third curve 52if present and flatter than second curve 50 in a three zone design.Fourth or peripheral curve 54 is generally structured to provideadequate edge lift and to aid in lens comfort, movement, tear and debrisexchange.

In the embodiment depicted in FIG. 4, back shaping zone 48 and secondcurve 50 are both displaced as compared to geometric center 56.According to another embodiment of the invention, back shaping zone 48is displaced relative to geometric center 56 while second curve 50shares its center with geometric center 56.

Referring now particularly to FIG. 5, another embodiment of displacedmolding zone contact lens 32 is depicted. Structures similar to thosedescribed above with relation to FIG. 4 are marked with similarreference numerals. In the depicted embodiment, stabilizing structures64 include superior thin zone 66 and inferior thin zone 68. Superiorthin zone 66 and inferior thin zone 68 are thinner than center zone 70.According to the depicted embodiment of the lens, orientation marker 72is also present. Orientation marker 72 may be located inferiorly,nasally or temporally or superiorly so long as it marks a knownorientation of displaced molding zone contact lens 32.

Referring now to FIG. 6, another embodiment of displaced molding zonecontact lens 32 is depicted. In the depicted embodiment, rigid curvedshell 34 of displaced molding zone contact lens 32 presents concavesurface 42 back shaping zone 48, second curve 50, optional third curve52 and fourth or peripheral curve 54. Rigid curved shell 34 presentsgeometric center 56. As can be seen in the depicted embodiment, shapingzone center 58 is displaced from geometric center 56 while second curve50 is centered on geometric center 56.

Referring now to FIG. 7, a cross sectional view of displaced moldingzone contact lens 32 is depicted. In this view, displaced molding zonecontact lens 32 presents convex surface 40, concave surface 42, overalldiameter 44, geometric center 56 and shaping zone center 58. Forclarity, various other zones and curves are not depicted in FIG. 7.

In operation, Displaced molding zone contact lens 32 is placed on cornea26 of eye 22. Displaced molding zone contact lens 32 is particularlyuseful for circumstances where the pupil or visual axis of the eye isdemonstrated to be displaced from the geometric center of the cornea 26.Displaced molding zone contact lens 32 orients so that back shaping zone48 is substantially centered on the pupil or visual axis of the eye whenthe pupil or visual axis is displaced. Accordingly, shaping zone center58 generally coincides with the visual axis or pupil center of eye 22.

Displaced molding zone contact lens 32 is expected to orient relativethe cornea to approximately center back shaping zone 48 on the pupil orvisual axis of the eye when the pupil or visual axis is displaced basedon alignment between the anterior corneal epithelium 28 and concavesurface 42.

Stabilizing structure 64, if present, including superior thin zone 66and inferior thin zone 68 are met with pressure from eyelids and thusare expected to tend to orient center zone 70 horizontally thusmaintaining orientation and location of shaping zone center 58substantially with the pupillary center or visual axis of eye 22.

If present, orientation marker 72 allows the contact lens wearer orpractitioner to determine proper orientation of displaced molding zonecontact lens 32 so that shaping zone center 58 substantially coincideswith the desired location.

The present invention may be embodied in other specific forms withoutdeparting from the spirit of the essential attributes thereof;therefore, the illustrated embodiments should be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than to the foregoing description to indicatethe scope of the invention.

Various embodiments of systems, devices, and methods have been describedherein. These embodiments are given only by way of example and are notintended to limit the scope of the claimed inventions. It should beappreciated, moreover, that the various features of the embodiments thathave been described may be combined in various ways to produce numerousadditional embodiments. Moreover, while various materials, dimensions,shapes, configurations and locations, etc. have been described for usewith disclosed embodiments, others besides those disclosed may beutilized without exceeding the scope of the claimed inventions.

Persons of ordinary skill in the relevant arts will recognize that thesubject matter hereof may comprise fewer features than illustrated inany individual embodiment described above. The embodiments describedherein are not meant to be an exhaustive presentation of the ways inwhich the various features of the subject matter hereof may be combined.Accordingly, the embodiments are not mutually exclusive combinations offeatures; rather, the various embodiments can comprise a combination ofdifferent individual features selected from different individualembodiments, as understood by persons of ordinary skill in the art.Moreover, elements described with respect to one embodiment can beimplemented in other embodiments even when not described in suchembodiments unless otherwise noted.

Although a dependent claim may refer in the claims to a specificcombination with one or more other claims, other embodiments can alsoinclude a combination of the dependent claim with the subject matter ofeach other dependent claim or a combination of one or more features withother dependent or independent claims. Such combinations are proposedherein unless it is stated that a specific combination is not intended.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims, it is expressly intended thatthe provisions of 35 U.S.C. § 112(f) are not to be invoked unless thespecific terms “means for” or “step for” are recited in a claim.

1. (canceled)
 2. A contact lens for application in practice oforthokeratology on an anterior corneal surface of an eye, comprising: acurved shell having a concave surface and a convex surface, the concavesurface including a carrier zone and a back shaping zone, the backshaping zone having a first spherical or toric curvature and the carrierzone having at least one second spherical or toric curvature differentfrom the first spherical or toric curvature; the curved shell adapted toshape an anterior corneal surface by physical interaction between theback shaping zone and the anterior corneal surface whereby refractiveerror of the eye is temporarily or permanently reduced; the curved shellhaving a geometric center and the back shaping zone having a shapingzone center, the back shaping zone center being offset peripherally fromthe geometric center; and the curved shell defines structure thatstabilizes rotation of the contact lens relative to the eye.
 3. Thecontact lens as claimed in claim 1, wherein the at least one secondspherical or toric curvature further comprises a second curve and thesecond curve is centered on the shaping zone center
 4. The contact lensas claimed in claim 1, wherein the at least one second spherical ortoric curvature further comprises a second curve and the second curve iscentered on the geometric center.
 5. The contact lens as claimed inclaim 1, wherein the contact lens is a reverse curve design.
 6. Thecontact lens as claimed in claim 1, wherein the contact lens comprises athree curve design.
 7. The contact lens as claimed in claim 1, whereinthe contact lens comprises a four curve design.
 8. The contact lens asclaimed in claim 1, wherein the overall diameter approximates a corneallimbal diameter of the eye to which the contact lens is to be applied.9. The contact lens as claimed in claim 1, wherein the overall diameteris in a range between 10.5 and 13.0 millimeters.
 10. The contact lens asclaimed in claim 1, wherein the overall diameter is in a range between10.5 and 12.5 millimeters.
 11. The contact lens as claimed in claim 1,wherein the overall diameter is in a range between 11.0 and 12.0millimeters.
 12. The contact lens as claimed in claim 1, furthercomprising an orientation marker thereon.
 13. The contact lens asclaimed in claim 1, wherein the structures that stabilize rotation ofthe contact lens relative the eye comprise a superior thin zone and aninferior thin zone.